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PENELLOPE. III. The peculiar accretion variability of XX Cha and its impact on the observed spread of accretion rates

R. A. B. Claes, C. F. Manara, R. Garcia-Lopez, A. Natta, M. Fang, Z. P. Fockter, P. Ábrahám, J. M. Alcalá, J. Campbell-White, A. Caratti o Garatti, E. Covino, D. Fedele, A. Frasca, J. F. Gameiro, G. Herczeg, Á. Kóspál, M. G. Petr-Gotzens, G. P. Rosotti, L. Venuti, G. Zsidi

The processes regulating protoplanetary disk evolution are constrained by studying how mass accretion rates scale with stellar and disk properties. The spread in these relations can be used as a constraint to the models of disk evolution, but only if the impact of accretion variability is correctly accounted for. While the effect of variability might be substantial in the embedded phases of star formation, it is often considered limited at later stages. Here we report on the observed large variation in the accretion rate for one target, XX Cha, and we discuss the impact on population studies of classical T Tauri stars. The mass accretion rate determined by fitting the UV-to-near-infrared spectrum in recent X-shooter observations is compared with the one measured with the same instrument 11 years before. XX Cha displays an accretion variability of almost 2 dex between 2010 and 2021. Although the timescales on which this variability happens are uncertain, XX Cha displays an extreme accretion variability for a classical T Tauri star. If such behavior is common among classical T Tauri stars, possibly on longer timescales than previously probed, it could be relevant for discussing the disk evolution models constrained by the observed spread in accretion rates. Finally, we remark that previous studies of accretion variability based on spectral lines may have underestimated the variability of some targets.

accretion, accretion disks / stars: pre-main sequence / stars: variables: T Tauri, Herbig Ae/Be / stars: individual: XX Cha

Based on observations collected at the European Southern Observatory under ESO programmes 084.C-1095 and 106.20Z8.

Astronomy & Astrophysics
Volume 664, Article Number L7, Number of pages 12
2022 August

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia